1. Field of the Invention
The present invention relates generally to a safety belt for automotive vehicles. Particularly, the present invention relates to a vehicle safety belt and buckle with emergency retraction capability.
2. Description of the Prior Art
In modern automotive technologies, emergency lock safety belt arrangements have been developed in various constructions. Emergency lock safety belt arrangements generally operate to lock a safety belt for preventing extraction of the belt in response to an extraordinary magnitude of deceleration which can be caused upon vehicle collision. Such a so-called, passive safety belt arrangement is generally successful in protecting a seat occupant from colliding into vehicular structural components during collision impact.
On the other hand, these arrangements tend to tightly restrict a seat occupant onto the seat even when no emergency condition exists. This may lead to discomfort and restricted freedom of movement of the seat occupant and may degrade riding enjoyment or, through discomfort, lead a vehicle occupant to neglect to use the safety belt entirely.
In order to address this situation, some modern safety belt arrangements are provided with a tension reducing capability to permit locking the safety belt at a position extracted in length to slightly more than that required for firmly restricting the seat occupant. This so-called active safety belt arrangement reduces tightness of the belt under normal driving conditions and improves riding comfort. For establishing an emergency lock function, a belt retractor is normally employed. The emergency lock safety belt retractor is sensitive to an inertial moment exerted on the vehicular body to establish locking of the safety belt when a length of the inertial moment exceeds a predetermined time. Some emergency lock safety belt retractors also employ a webbing sensor, which senses an extraction speed of the safety belt, to establish locking when the belt extraction speed is extraordinary high. With such an arrangement, locking is necessarily established after extraction of a certain length of belt.
As such arrangements allow a greater degree of slack, a certain magnitude of movement is available to the seat occupant. Particularly when the safety belt arrangement employs the aforementioned reduced tension arrangement, a magnitude of movement allowed the seat occupant in response to extraordinary deceleration becomes greater. As can be appreciated, upon vehicular collison, it is preferred to restrict the seat occupant to the seat as firmly as possible. Therefore, advanced safety belt systems utilize such types of arrangements in combination with a pre-loader which forcingly retracts the belt for firmly restricting the seat occupant with increased tension upon collision, or with an air bag system which forms an air cushion for preventing the seat occupant from colliding with vehicular structural components located in front of the seat. One example of such a pre-loader mechanism is disclosed in Japanese Patent Application First Publication (Unexamined) Showa 57-128169, for example.
Such additional equipment of course necessitates added production costs. In order to avoid these, there has been proposed mechanical buckle pretensioners which draw a safety belt buckle in a tensioning direction to provide additional tension for the belt. Such types of mechanical buckle pre-tensioners have been disclosed in Japanese Patent Application First (unexamined) Publications Nos. 61-241234 and 62-289451, for example. The mechanical buckle pre-tensioner employs a trigger mechanism for causing pre-tensioning operation in response to collision shock. However, the trigger mechanism is relatively bulky. Since the trigger mechanism needs to be associated with the safety belt buckle, it must be positioned proximate the buckle. Due to the bulky nature of the mechanism, this causes interference with the positioning of vehicle structural components, such as a console box, and so forth. Furthermore, since modern vehicle seats usually employ a reclining mechanism for adjusting a seat angular position, in addition to the safety belt mechanism, the structural assembly around the seats become complicated and difficult to install, increasing the space and expense required as well as the weight of the vehicle.